Radar sensors in motor vehicles are used for measuring the distance and/or speed of objects. Known, for example, are driver assistance systems in the form of cruise controllers for motor vehicles, which use a radar system in order to locate a vehicle driving ahead and to measure the distance to this vehicle. Such a distance control system is also referred to as an ACC system (adaptive cruise control).
To ensure the proper functioning of radar sensors, the sensors must be aligned within predefined limits in relation to the roadway or the desired detection range, for example after their installation in the vehicle. For instance, a radar sensor of an adaptive cruise control system usually requires an alignment of a main radiation direction at a precisely defined elevation angle, also known as elevation, and a precisely defined lateral angle to the longitudinal vehicle axis, for example parallel to the longitudinal vehicle axis. Such an alignment, for example, makes it possible to compensate for production-related tolerances of the mechanical components of the radar sensor, and for tolerances that arise in the fastening to the motor vehicle.
German Patent No. 196 42 811 describes a radar system having transmit/receive elements and a housing, which is sealed by a radar lens in the radiation direction. Two mirror-reflective areas are applied at the front side of the housing, outside the beam path of the electromagnetic waves. They can be produced by vapor deposition of a reflective layer or by bonding a reflective foil, for instance. For the adjustment, laser beams are directed onto the reflective areas, and a directional antenna of the radar system is adjusted in such a way that the reflected laser beams illuminate predefined target markings.